Canister type filters are commonly used for removing particulate matter from lubricating oils, and are attached to the lubricated machine to continuously filter the oil while the machine is operating. Widely used on motor vehicle engines, such filters are typically discarded after only 100-300 hours of use because of clogging. Canister type disposable filters are also used on other industrial equipment including gas compressors and hydraulic systems for cleaning lubricants and hydraulic fluids.
Another use of canister-type filters is the removal of particulate matter from water. For example, such filters may be found in homes and industry for removing sand, grit, rust and purification chemicals from municipal water supplies.
The useful life of such filters is limited by the rate at which the pressure drop across the filter element increases due to clogging by particulate matter. All of the particulate matter removed by the filter element remains on or in the element, which provides little storage capacity for such contaminants. A short filter life results.
Common disposable canister filters have a closed cylindrically shaped canister with the inlet and outlet at the upper end, or face. The filter outlet is an internally threaded coupling centrally located in the face, and is screwed onto a threaded nipple in a matching face on the filter receptacle on the engine or other fluid using apparatus. Filter inlet holes encircle the filter outlet and accept contaminated fluid from corresponding ports in the filter receptacle which lead from the engine. A narrow elastomeric seal on the filter face encircles the inlet holes. When the filter outlet is screwed onto the corresponding nipple, the seal is compressed between the matching faces to prevent leakage of fluid.
The filter element is generally annular, with fluid flowing from the exterior surface toward the central axis. Various filter media materials can appropriately be used, and may be adapted depending upon the type of filtration practiced.